The objective of this application is to develop statistical models for anthrax outbreaks and the pathogenesis of inhalation anthrax. Because of limited laboratory and field study data on inhalation anthrax relative to other diseases, it is imperative to glean as much information as possible from the available data through development and application of state-of-the-art statistical methods and mathematical and statistical models. There are three specific aims: 1. Develop statistical models for anthrax outbreaks. These models would allow one to estimate the size of an anthrax outbreak, the impact of antimicrobial prophylaxis, the probability that an outbreak has ended, and the likely date cases were exposed to the spores. The methods will be applied to the 2001 U.S anthrax outbreak. The performance and operating characteristics of the methods will be evaluated by computer simulation. The methods will be extended to develop statistical algorithms that could be used to forecast and characterize future anthrax outbreaks. 2. Develop statistical and mathematical models for the incubation period distribution of inhalation anthrax that account for dependence on age and numbers of inhaled spores. These models will be based on reanalysis of the Sverdlovsk outbreak in 1979 as well as other published experimental and field studies. 3. Perform sensitivity analyses to underlying assumptions of the proposed models and methods, and, quantify the statistical error in the results. This work will address sensitivity of the results to the parametric form of the incubation period distribution, confidence interval procedures for parameters, and impact of phenomenon such as resuspension of spores or prolonged spore circulation in the atmosphere. This work will depend on results from specific aims 1 and 2.